Sulfur-containing polymers, particularly polysulfides, are widely used in the aerospace, construction, and insulating-glass industries. They generally offer good solvent resistance, water-immersion resistance, shrink resistance, and good adhesion to glass, metal, and concrete.
Polysulfides are made by reacting bis(chloroethyl)formal, sodium polysulfide, and a small amount of trichloropropane to make a high molecular weight branched polysulfide. This product is then degraded with sodium hydrosulfide and sodium bisulfite to make a mercaptan-terminated polymer having a molecular weight within the range of about 1000 to 8000. The mercaptan-terminated polymer is then reacted with an oxidant such as lead dioxide or manganese dioxide to produce a cured polysulfide sealant.
Other types of sulfur-containing polymer sealants are made from mercaptan-terminated polyurethanes, and polythioethers. These polymers often cure by a polysulfide-type crosslinking mechanism. These other sulfur-containing polymer sealants are also used primarily in the aerospace, construction, and insulating-glass industries.
Cured sulfur-containing polymer sealants are difficult to remove from glass or metal surfaces with commercially available hand-wipe cleaners and common organic solvents. Even solvents that are reasonably good for coating removal, e.g., methylene chloride, are relatively ineffective on cured polysulfide sealants and pose toxicity, handling, and/or environmental concerns.
Still needed in the industry is a method for removing cured sulfur-containing polymer sealants from glass, aluminum, and other surfaces. Preferably, the method would quickly and completely soften and remove these sealants, and would use a low-toxicity, water-rinsable remover.